Pipette provided with sampled volume adjusting means

ABSTRACT

The sampling pipette includes means for adjusting the volume of liquid to be taken. It includes a locking element that is movable between an inactive position in which it makes the adjustment means unsuitable for performing adjustment and an active position in which it makes the adjustment means suitable for performing adjustment.

The invention relates to pipettes for sampling liquids.

Document FR-2 696 110, for example, discloses a sampling pipette havinga knurled wheel accessible through a window in the body of the pipettein order to adjust the volume of liquid to be taken. The volume is alsoindicated on a display. That pipette presents numerous advantages. Theknurled wheel does not project outside the body of the pipette and istherefore relatively unlikely to be actuated involuntary. In addition,while it is being driven, the knurled wheel is braked by means of afriction assembly which further reduces any risk of losing adjustment.Nevertheless, it is desirable to improve it further. There remains asmall risk of the volume to be taken being accidentally altered byinvoluntary action on the knurled wheel.

It is therefore desired to eliminate any risk of accidental alternationto the volume that is to be taken.

Document U.S. Pat. No. 5,849,248 discloses a pipette having a lockingelement that is movable between an inactive position in which itprevents the adjustment means from performing adjustment, and an activeposition in which it allows them to perform adjustment. That elementextends close to a volume-adjusting knob. There is therefore no need tofear any unwanted change to the volume to be taken.

An object of the invention is to provide a pipette of a type that isdifferent but that also avoids unwanted change of adjustment.

According to the invention, this object is achieved by providing asampling pipette including means for adjusting the volume of liquidtaken as a sample, said means comprising at least one adjustment controlmember, the pipette including a locking element movable between aninactive position in which it makes the adjustment means unsuitable forperforming adjustment and an active position in which it makes theadjustment means suitable for performing adjustment, the locking memberbeing the adjustment control member.

Thus, when the locking element is in the inactive position, it is notpossible accidentally to change the adjustment of the volume to betaken. In addition, this elimination of any risk of loss of adjustmentmakes it possible in return to eliminate or reduce the friction brakingon the knurled wheel, thereby making it easier to turn when making anadjustment voluntarily. This elimination is all the more welcome sincewith the prior art pipette of document FR-2 696 110, it is possible forthe user's glove to become pinched between the wheel and the body of thepipette while turning the wheel. This drawback can thus likewise beeliminated.

Furthermore, the pipette of the invention enables a single lockingelement to be used for all of the successive operations associated withadjustment, e.g. unlocking, volume adjustment, and locking.

The invention may also present at least any one of the followingcharacteristics:

-   -   the locking element is slidably movable between the two        positions;    -   the locking element is arranged to be driven directly from one        of the two positions to the other by a user;    -   the locking element extends inside a body of the pipette;    -   the pipette is arranged in such a manner that the locking        element is suitable for transmitting an adjustment movement to a        member of the adjustment means when in the active position, and        is unsuitable for performing such transmission when in the        inactive position;    -   the pipette is arranged in such a manner that the locking        element is suitable for transmitting movement from one to the        other of two members of the adjustment means other than the        locking element when in the active position, and is unsuitable        for performing said transmission when in the inactive position;    -   the movement is a turning movement;    -   the adjustment means comprise two members arranged to be        positively engaged with each other when the locking element is        in the active position, and to be disengaged from each other        when the locking element is in the inactive position;    -   the pipette has two adjustment control members;    -   the pipette includes a sampling control knob forming an        adjustment control member;    -   the pipette includes return means for returning the locking        element into the inactive position;    -   the pipette has means for holding the locking element in the        inactive position against the return means;    -   the pipette is arranged in such a manner that the locking        element is suitable for passing from the active position to the        inactive position by passing through a hard point; and    -   the adjustment means comprise a driving member and a driven        member suitable for being driven by the driving member via at        least one complementary shape connection, one of the driving and        driven members being deformable so as to interrupt the        connection when it is subjected to intense urging exceeding a        predetermined intensity.

Other characteristics and advantages of the invention appear furtherfrom the following description of a preferred embodiment and of avariant given as non-limiting examples. In the accompanying drawings:

FIG. 1 is a fragmentary axial section view of a pipette constituting apreferred embodiment of the invention;

FIG. 2 is a perspective view of a portion of the adjustment mechanism ofthe FIG. 1 pipette;

FIG. 3 is a larger scale view of the FIG. 2 mechanism;

FIG. 4 is an axial section view of the FIG. 2 mechanism;

FIG. 5 is a perspective view of a sub-portion of the FIG. 2 mechanism;

FIG. 6 is an elevation view of the FIG. 5 sub-portion;

FIG. 7 is a perspective view of the positive clutch and the driver ofthe FIG. 4 mechanism;

FIGS. 8 to 11 are four fragmentary views in axial section showing thevarious stages of co-operation between the adjustment knob and thecoupler of the FIG. 4 mechanism;

FIG. 12 is a cross-section view of the FIG. 6 sub-portion on planeXII—XII;

FIG. 13 is an exploded section of certain elements of FIG. 12;

FIG. 14 is a section view of the adjustment screw on its own;

FIGS. 15 to 18 show various stages of co-operation between the elementsof FIG. 12; and

FIG. 19 is a view analogous to FIG. 12 showing a variant embodiment ofthe invention.

The sampling pipette of the present embodiment of the invention is ofthe same type as that of document FR-2 696 110. Reference shouldtherefore be made to that document for certain details of the pipettealready disclosed therein. Only certain aspects of the volume-adjustingmechanism are described in detail herein.

In conventional manner, the pipette 2 comprises a body 2 serving as ahandle to be held in the hand of the user. The pipette has a piston (notshown) slidably movable along a longitudinal axis 10 of the pipetteinside a bottom cavity of the pipette in order to suck a volume ofliquid to be taken into said cavity or in order to expel the liquidtherefrom. Piston displacement is controlled in particular by means of acontrol rod 4 of axis 10 having its bottom portion connected to thepiston via parts of conventional type and not shown. At its top end, therod 4 is surmounted by a pushbutton 6 rigidly fixed to the rod suitablefor being actuated by the user using the thumb of the hand that isholding the pipette. This causes the piston to move down or up as afunction of the corresponding movement of the knob. The pipette includesa return spring suitable for returning the piston and the rod to thehigh position at the end of their down stroke for expelling liquid, anda purge spring whose effect is added to that of the return spring whenthe stroke of the piston is continued downwards for a purge stroke.

The volume to be taken during a normal full stroke of the piston, notincluding any purge stroke, can be adjusted by means of an adjustmentknob 8 in the form of a ring, and by means of the pushbutton 6. Thesetwo knobs are mounted so as to be capable of turning about thelongitudinal axis 10 of the pipette. Turning either of these knobscauses and adjustment screw 5 that is coaxial with the rod 4 to turnabout the axis 10. The way in which turning the adjustment screw 5causes the volume to be taken to vary is conventional and is notdescribed. There follows a detailed description of the top portion ofthe adjustment mechanism.

All of the parts described below are symmetrical about the axis 10unless otherwise specified.

With reference to FIGS. 1 to 4, the pipette has a coupler 12 slidablymounted on the rod 4 but constrained to turn together therewith. Forthis purpose, the coupler presents a central top orifice presentingthree radial tabs 14 engaging in three longitudinal grooves 16 in therod 4. This orifice is formed by a top washer 18 of the coupler. Thecoupler has three arms 20 extending downwards parallel to the axis 10away from the washer 18. Each arm 20 is generally flat in the directionextending radially to the axis 10, and on its face 22 facing away fromthe axis it presents an elongate portion in relief 24 extending in thecircumferential direction of the axis 10.

The adjustment knob 8 is slidably movable along the axis 10 and can beturned about said axis. It is essentially cylindrical in shape about theaxis 10. The outside face 26 of this adjustment knob is accessible tothe user via windows in the body to enable the adjustment knob to bemanipulated. For this purpose, the adjustment knob has portions inrelief for gripping purposes. Close to its top circular edge, theadjustment knob 8 has three forks 30 projecting radially towards theaxis. These forks are in the form of female U-shapes open towards theaxis, and they are complementary in shape to the profiles of the arms20, receiving respective ones of them.

It follows from the above arrangement that the adjustment knob 8 isconstrained to turn with the coupler 12 but that it is not fixed theretoin sliding. The adjustment knob 8 can occupy both a low or inactiveposition constituting a locked position, and a high or active positionconstituting an unlocked position. These two positions are independentof the angular position of the adjustment knob 8 about the axis. Theadjustment knob moves from one position to the other by sliding alongthe axis. The coupler 12 has an annular spring 25 about the axis 10pressing radially against the inside faces of the arms 20 to urge themradially away from the axis.

In the low position, as shown in FIGS. 1 to 4, and 8, the arms 20, butnot the portions 24 in relief, are received in the forks. The sameapplies in the high position as shown in FIG. 11. On passing from oneposition to the other, as shown in FIGS. 8 to 11, the portions in relief24 are received in the forks and cause the arms 20 to flex temporarilyin a radial direction. This leads to an audible click and provides ahard point during manipulation, thus informing the user about changesbetween the high and low positions. In addition, the portions 24 inrelief hold the knob in the high position against the return spring,unless contrary action is exerted by the user.

With reference to FIGS. 1, 4, and 7, the pipette has a positive clutch32 of generally cylindrical shape presenting an outer annular peripheralrib 34 approximately at half-height. The adjustment knob 8 comprises twocylindrical parts 8 a and 8 b constituting a top part and a bottom partthat are engaged as force-fits on the outside of the clutch 32 and thatbear axially against the rib 34. The adjustment knob 8 is rigidlysecured to the clutch. On its outside face, as shown in detail in FIG.7, the clutch has portions in relief that co-operate with complementaryportions in relief on the adjustment knob in order to provide said rigidconnections. The clutch 32 has a set of teeth 36 extending close to itstop edge, projecting radially from its inside face towards the axis.

The pipette has a driver 38 with a top portion 40 of cylindrical shapeprovided with a plurality of teeth 42, e.g. two teeth, extending closeto its top edge, projecting from its outside face radially away from theaxis. These two teeth are suitable for engaging with the set of teeth 36in the clutch when they are at the same height along the axis 10 as theset of teeth.

The driver 38 can be moved relative to the adjustment screw 5. Itextends directly in register therewith in a radial direction. Unlike theadjustment screw 5 which is free to turn helically about the axis 10,the driver 38 is prevented from sliding along the axis 10 relative tothe body of the pipette. For this purpose, its top portion is blocked bya spacer 44 and its bottom portion is blocked by a part 46, as shown inFIG. 1.

With reference in particular to FIGS. 5, 6, and 12, the driver 38 hastwo main tabs 48 and two secondary tabs 50 extending parallel to theaxis 10 downwards from the top portion 40. The secondary tabs 50 are inthe form of cylindrical sectors about the axis 10. They alternate aroundthe axis with the main tabs 48. The main tabs 48 have cylindricaloutside faces and inside faces that are plane, from which there projectrespective splines 52 of rectangular section extending parallel to theaxis 10. The driver 38 has a spring 54 surrounding the outside of thefour tabs 48, 50 and received in outside notches thereof. The springtends to urge the tabs radially towards the axis.

The adjustment screw 5 is hollow and has the control rod 4 passinglongitudinally therethrough. These two parts are completely independentconcerning relative movement. The adjustment screw 5 is generallycircularly symmetrical. Nevertheless, and more precisely, the adjustmenthas two flats 56 that are parallel to each other and to the axis 10 onopposite sides of said axis. These flats extend over a middle portion 58of the adjustment screw extending above a bottom portion 60 of theadjustment screw that is threaded and serves to adjust volume. The flats56 are connected to each other via circular arcs 61. The adjustmentscrew also has two longitudinally extending ridges 62 parallel to theaxis 10, extending from the edges of respective flats so as toconstitute abutments when going circumferentially around the outsideface of the adjustment screw 5 away from the flats, and also so as topresent circular arcs that do not form abutments going away from thecylindrical zones 61.

The two ridges 62 are not symmetrical to each other about the axis 10,but they are symmetrical to each other about a midplane of the screwparallel to the two flats. In addition, the two ridges 62 do notcoincide exactly with each other in position along the axis 10. Theyoverlap over a certain length. However, one of the ridges extends higherthan the other whereas said other ridge extends further down than thefirst. The two ridges thus overlap in part along the axis 10. Thelongitudinal position of the second ridge, normally hidden in FIG. 6, isnevertheless represented by a line 56.

The driver 38 may be coupled to turn with the adjustment screw 5, or itmay be decoupled therefrom.

When coupled, as shown in FIGS. 12 and 15, the driver is situated at alevel along the adjustment screw where the two ridges 62 overlap. Thesecondary tabs 50 press against the cylindrical zones 61 and arecomplementary in shape thereto. They co-operate therewith to formsurface-on-surface contact. The splines 52 bear radially against theflats 56 and come into abutment against the respective ridges 62. Thespring 54 holds the four tabs pressed against the adjustment screw 5,and in particular it keeps the splines engaged against the ridges.Consequently, any turning movement of the driver 38 can be transmittedto the adjustment screw 5. Since the driver, unlike the adjustment screw5, is prevented from sliding along the axis, such turning causes theadjustment screw to slide along the axis, with the adjustment screwmoving helically. These two parts are thus coupled to turn about theaxis by means of friction forces, and above all by means of the ridgesand the splines. Torque is thus transmitted even against a high level ofopposing torque.

The ridges 62 are positioned in such a manner that in the vicinity ofeach top and bottom end-of-stroke positions of the adjustment screw 5,the ridge which serves to transmit movement towards said abutment isinterrupted, as shown in FIGS. 14 to 18. As a result, over the entireremaining stroke to be traveled before reaching the abutment position,torque transmission takes place only via friction forces between thetabs and the adjustment screw. Under such conditions, transmission takesplace only if the magnitude of the connection forces, and thus themagnitude of the opposing torque, is less than a predetermined valuewhich is a function of the spring 54. This transmission neverthelesstakes place so that the user can continue to manipulate the driver 38(indirectly as described below) in order to drive the adjustment screw5. Once the adjustment screw 5 reaches the end of the adjustment stroke,the opposing torque becomes infinitely large and breaks the connectionvia the friction forces. In spite of the return effect of the spring 54,the main tabs 48 then splay apart so as to move off the flats and ontothe zones 61 in order to follow the shape of the adjustment screw, thusallowing the driver 38 to turn on its own. The adjustment screw 5 isthus subjected to little force and remains stationary. The bottomportion 60 of the adjustment screw 5 is thus protected against excessiveforce.

If the user seeks to drive the adjustment screw 5 in the oppositedirection away from this position, it suffices to turn the driver 38 inthe opposite direction. Within less than half a turn, one of the splines52 meets the other ridge 62 and the two parts are again connected toturn together, but in the opposite direction. The same operation occursin the vicinity of the other end of the adjustment stroke.

The operation of the adjustment knob 8 is described below.

The knob is shown in its low, inactive, and locked position in FIGS. 1,3, and 4. The arms 20 are in engagement with the adjustment knob 8. Inthis position, the teeth 36 of the clutch are out of engagement with theteeth 42 of the driver 38. Any movement of the adjustment knob 8 is thusprevented from turning the driver 38 or the adjustment screw 5. This lowposition of the adjustment knob 8 thus causes the adjustment means to beinactive. The volume to be taken therefore cannot be modified eithervoluntarily or involuntarily. The word “locked” written on the outsideface 26 of the adjustment knob 8 appears in the window where it can beseen by the user. A return spring 63 shown in FIG. 1 bears axiallyupwards against the coupler 12 and downwards against the adjustment knob8, thereby urging the adjustment knob so as to keep it in this lowposition.

If the user desires to adjust the volume, then the adjustment knob 8must be slid upwards against the return spring 63 so that the forks 30go past the portions 24 in relief, thereby producing a click and a hardpoint. The adjustment knob is then in its high, active, and unlockedposition. It is held in this position by the portions 24 in relief untilthe user applies an opposing force. While in this position, the teeth 36of the clutch are engaged with the teeth 42 of the driver 38. Anyturning action applied by the user directly to the adjustment knob 8 orto the pushbutton 6 is thus transmitted via the teeth 36, 42 to thedriver 38, and then to the adjustment screw 5, providing it is notalready at the end of its stroke in the desired adjustment direction.Once the desired sampling volume has been set, the user can slide theadjustment knob 8 back into its low position to prevent any untimelyloss of adjustment.

In the above-described pipette, it should be observed that the driver 38is clamped against the adjustment screw 5, i.e. these parts are thusclutched or declutched in a manner that is automatic and not due todirect action taken by the user on these parts. In addition, the usernever acts directly on the adjustment screw 5.

Provision can be made for that one of the adjustment screw 5 and driver38 which is deformable in order to interrupt the connection between themto be the adjustment screw 5.

FIG. 19 shows a variant embodiment in which numerical references plus100 are given to elements that are analogous. The rod 104 is not shown.

In this variant, the splines 152 have a profile which is V-shaped with arounded tip. The flats 156 are replaced by V-grooves 156 having the sameV-angle as the splines so as to enable the screw 105 to be driven by thedriver 138. In the vicinity of the abutment positions, the respectivegrooves flare so as to increase the slope of one of their two faces.This face forms a ramp. The pipette is arranged in such a manner thatonce the end-of-stroke position is reached, the clamping force of thespring is insufficient to hold the splines 152 in the grooves 156. Theramp then causes the splines to escape from the grooves and the maintabs 148 to be splayed apart such that the driver no longer drives thescrew and continues to turn on its own.

The pipette may include electronic display means (e.g. liquid crystalmeans) for displaying a parameter relating to the operation of thepipette. For example, these means may continuously indicate the lockedor unlocked state of the knob 8.

1. An adjustable volume sampling pipette comprising: (a) a pipette bodyhaving a longitudinal axis; (b) an adjustment screw disposed inside thepipette body, the adjustment screw capable of turning to adjust a volumein the pipette; and (c) an adjustment knob, wherein the adjustment knobis accessible to a user via a window in the pipette body, and furtherwherein the adjustment knob is movable between an active position inwhich a turning action applied to the knob is transmitted to theadjustment screw and an inactive position in which a turning actionapplied to the adjustment knob is prevented from turning the adjustmentscrew.
 2. The pipette of claim 1 wherein the adjustment knob is slidablymovable between the active position and the inactive position in adirection parallel to the longitudinal axis of the pipette.
 3. Thepipette of claim 1, further comprising a rod coupled to the adjustmentknob and passing longitudinally through the adjustment screw.
 4. Thepipette of claim 3, further comprising a pushbutton mounted to the topend of the rod.
 5. The pipette of claim 3, wherein the rod is coupled tothe adjustment knob by a coupler that is slidably movable along the rodand constrained to turn with the rod.
 6. The pipette of claim 5, whereinthe coupler comprises a washer having a central orifice and at least onetab extending radially into the orifice and the rod comprises at leastone longitudinal groove along its length and further wherein the rodextends through the orifice such that the at least one tab engages theat least one groove.
 7. The pipette of claim 6 wherein the washerfurther comprises at least one arm extending downwards away from thewasher and the adjustment knob further comprises at least one forkprojecting radially toward the longitudinal axis and further wherein theat least one fork receives the at least one arm.
 8. The pipette of claim7 wherein the at least one arm further comprises an elongate portion inrelief extending away from the longitudinal axis and further wherein theportion in relief is received by the at least one fork when theadjustment knob passes from the active position to the inactive positionto produce an audible click.
 9. The pipette of claim 7 wherein thecoupler further comprises an annular spring pressing against the atleast one arm to urge the at least one arm away from the longitudinalaxis.
 10. The pipette of claim 5 wherein the adjustment knob isconstrained to turn with the coupler but is not constrained to slidewith the coupler.
 11. The pipette of claim 1, further comprising: (d) aclutch having a generally cylindrical shape onto which the adjustmentknob is mounted, the clutch comprising an outside face, an inside faceand teeth projecting radially from its inside face toward thelongitudinal axis; and (e) a driver, having a cylindrical shape,disposed around a portion of the adjustment screw and extending into theclutch, the driver comprising a top portion with an outside face andteeth extending radially from the outside face away from thelongitudinal axis; wherein the teeth on the driver are positioned toengage the teeth on the clutch when the adjustment knob is in the activepositioned but not when the adjustment knob is in the inactive position.12. The pipette of claim 11, wherein the driver further comprises tabsextending downwards from the top portion, the tabs comprising insidefaces and splines projecting from the inside faces and the adjustmentscrew comprises a middle portion above a threaded bottom portion, themiddle portion having an outside face and longitudinally extendingridges along the outside face and further wherein a turning movement ofthe driver causes the splines to come into abutment with the ridges totransmit the turning motion to the adjustment screw.
 13. The pipette ofclaim 12, further comprising a spring surrounding the outside of thetabs.
 14. The pipette of claim 12 wherein the splines and the ridgescomprise a complementary shape connection.
 15. The pipette of claim 14wherein the complementary shape connection is interrupted in a vicinityof a top end-of-stroke position of the adjustment screw or a bottomend-of-stroke position of the adjustment screw.
 16. The pipette of claim11, wherein the driver further comprises tabs extending downwards fromthe top portion, the tabs comprising inside faces and splines projectingfrom the inside faces and the adjustment screw comprises a middleportion above a threaded bottom portion, the middle portion having anoutside face and grooves along the outside face and further wherein aturning movement of the driver causes the splines to come into abutmentwith the grooves to transmit the turning motion to the adjustment screw.